It infects the skin and mucous membranes of the genitals or rectum, but it can also appear in areas such as the mouth, particularly the lips.

It's quite a lot more common in women than in men. Its chief symptom is an outbreak of small blisters, and these can be very painful.

It's transmitted primarily through physical and sexual contact. During birth, the presence of herpes simplex virus in the birth canal can be a serious threat to the baby.

HIV and AIDS

HIV (which stands for 'Human Immunodeficiency Virus') is the germ which can cause AIDS – a potentially lethal disease. AIDS attacks the body's immune system, making the affected person very vulnerable to all sorts of infections.

In 2015, there are thought to be about 100,000 people with HIV living in the United Kingdom. A third of these are women.

Many people with HIV are heterosexual and have caught the infection through ordinary (vaginal) intercourse.

However, it is believed that about 41,000 of the UK total are gay men.

Another 32,000 HIV-positive people who were born in Africa are thought to have acquired the virus through 'straight' (vaginal) intercourse.

And if you're thinking of having sex (whether 'straight' or gay) while abroad, please take note of the fact that in some countries – particularly those south of the Sahara – HIV rates are very high. In South Africa, 11 per cent of the population are HIV-positive.

A very small number of British HIV sufferers have been intra-venous drug users, and caught the virus from contaminated needles.

A further small group of people got the virus through receiving infected blood transfusions overseas.

And in addition, about 1,200 British haemophiliacs caught HIV from contaminated blood products in the period 1978 to 1985. About 400 of them are still alive.

Public Health England estimates that in the UK as a whole, there are currently about 25,000 men and women who have HIV – but who don't yet know it. So, if you've taken a risk, get yourself a test!

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New cases of HIV

In 2013, about 6,400 new cases of HIV were diagnosed in the UK. About three-quarters of them were men, and a quarter were women.

Around 48 per cent of those who were diagnosed with HIV last year were men who have sex with men (MSM).

However, about 47 per cent of those who caught HIV acquired the virus through heterosexual (male-female) contact. So beware of thinking that 'straight' sex carries no risk!

Outlook in HIV infection

Some of those who are HIV-positive will go on to develop AIDS.

In Britain, there were 530 deaths from AIDS in 2013 (400 men and 130 women). However, it's important to realise that the death rate from HIV has dropped massively in recent years – thanks to effective therapy.

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If you get diagnosed and treated early, you may well have a normal life expectancy.

Genital warts

In 2013, English GUM clinics saw about 74,000 new cases of genital warts. Many other people develop warts, but don't attend clinics.

These warts are caused by the human papilloma virus (HPV), which is passed on during sex.

Many months can pass from the time of infection to the actual development of warts, so it may be very difficult to determine who you got them from.

In women, HPV can lead to microscopic changes in the cervix and then to the development of cervical cancer.

HPV is now thought to be associated with various other cancers, including carcinoma of the anus and also of the throat and adjoining regions.

In 2015 it seems increasingly likely that many cases of throat cancer are caused by HPV infection during oral sex.

Syphilis

In 2013, the incidence of syphilis went up by about nine per cent.

Almost 3,250 cases were seen at English GUM clinics. About three-quarters of all cases occurred in men who have sex with men (MSM).

If left untreated, syphilis is a dangerous and life-threatening disease. It's caused by a corkscrew-shaped germ called Treponema pallidum.

It's passed on by intercourse or by almost any other form of sexual interaction, including anal sex.

The first symptom appears between 9 and 90 days after exposure to the germ that causes it.

A small lump develops at the infection site (usually the penis, the anus or the vagina), and this soon breaks down to form a painless ulcer.

Later, there is a secondary stage (characterised by fever, rashes and throat ulcers), and eventually a tertiary stage (in which the germ may attack the brain, spinal cord and other organs).

Non-specific genital infection

This rather 'catch-all' term means any sexual infection of the genitals in which a causative germ has not been found. Many cases are actually caused by chlamydia.

The diagnosis of 'non-specific genital infection' is mostly made in men. It is frequently referred to as 'non-specific urethritis' or 'NSU'. Chief symptoms are pain in passing urine, and a slight discharge from the penis.

Currently, around 54,000 men a year attend English GUM clinics because of NSU.

Trichomonas

Trichomonas vaginalis (often known as 'TV') is a protozoan 'bug' that affects the vagina.

It causes a green or yellowish, bubbly vaginal discharge and intense vulval soreness. It often produces a 'fishy' smell.

However, some women have no symptoms at all, and men rarely do.

For unknown reasons, the incidence of 'TV' in the UK has declined sharply in recent years, though it is reported as still being common in the USA.

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Only about 6,000 cases were diagnosed in UK clinics last year. But in addition, a substantial number were treated by GPs.

Bacterial vaginosis

The diagnosis of bacterial vaginosis (BV) has become common during the last 10 years, with about 100,000 women per year being seen in GUM clinics, and an unknown number being treated elsewhere.

BV is a common cause of vaginal discharge. The discharge is usually whitish or greyish or sometimes yellowish, and tends to have an off-putting 'fishy' odour.

Unlike the discharges caused by thrush or trichomonas, it's not usually associated with soreness, discomfort or itching.

It's uncertain if BV is transmitted sexually, especially as there's no equivalent condition in males. It respond well to the antibiotic metronidazole.

It's impossible to say precisely how common it is, since it's not only treated in GUM clinics but also in GPs' surgeries and Family Planning clinics.

Furthermore, huge numbers of women simply treat it themselves. These days anti-thrush treatment is available without prescription in every pharmacy in Britain.

At a conservative estimate, there must be at least half a million thrush infections per year in Britain.

Candida is a fungal infection. It loves warm, moist conditions, which is why it flourishes in women's vaginas – and also in babies' mouths, particularly in the newborn.

I'd like to stress that it's NOT an STD, and many people don't regard it as a sexually transmitted infection at all – though undoubtedly partners do sometimes pass it to and fro between them.

That's why it's sometimes necessary to treat the male, as well as the female, in order to eradicate the candida from the relationship.

Scabies

At the moment, at least 2,400 new cases of scabies and crabs are seen each year in GUM clinics..

Scabies ('the itch') isn't actually a genital infection. But it's often dealt with at GUM clinics because of the fact that it's frequently acquired through being in bed with someone who has the condition.

Crabs (pubic lice)

Various kinds of lice affect humans. But the type that are associated with sex are pubic lice, which are easily transmitted from one person to another when two sets of pubic hair meet.

If you catch crabs from someone, you'll find that you have intense itching in your pubic area. By looking carefully, you may be able to see the tiny greyish lice crawling around. They do look a bit like minute crabs.

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It may be easier for you to spot the white eggs (nits) that stick to the hairs.

Molluscum contagiosum

Molluscum contagiosum is a viral condition that causes little 'pearly,' flesh-coloured bumps on the skin.

It's known to many parents as a childhood condition that's passed on when children have skin-to-skin contact in baths or beds. But it can also affect adults – because it may be transmitted when you share a bed with somebody.

Over 17,000 cases turn up in GUM clinics every year: about 12,000 men and 5,000 women.

How can sexually transmitted diseases be avoided?

The fewer sexual partners a person has, the lower the risk of infection.

Most sexually transmitted diseases can be avoided to a large extent by practising safe sex (e g using condoms).

You should try not to have casual sex.

If you're under the influence of alcohol or other drugs, don't even consider having sex with anyone!

Most sexually transmitted diseases can be cured if they are diagnosed and treated in their early stages.

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How many people go to GUM clinics?

Currently, the number of people who go to GUM clinics is around two million per year. This figure has more than doubled since 2001.

Although most of them do not turn out to have an infection, the actual number who have STDs is currently around half a million per year in the UK.

Furthermore, a lot of genital infections are treated by GPs or private clinics – and these don't even get included in the national statistics that have been quoted above.

Generally speaking, if you think you have an infection you should go to a GUM clinic.

How do you find a GUM clinic?

Unfortunately, it's always been difficult for people to find a GUM clinic, simply because of the veil of secrecy that has traditionally surrounded this subject.

Regrettably, the government's NHS Direct phone line – which offered a complete list of STI clinics – has now been abolished.

You may find clinics listed in phone book directories under either 'genito-urinary medicine' or 'sexual health clinics'.

A better approach is to call your nearest hospital and ask them where the GUM or 'genito-urinary' clinic is located, and what the phone number is.

Alternatively, you can use the excellent Family Planning Association (FPA) clinic-finder. Just go to the FPA website, and check their helpful 'Find-A-Clinic' feature. Then tap in your postcode.

To visit a GUM clinic, you don't need a GP's letter or 'permission' from your doctor. Also, the clinic will not write to your GP, unless you specifically ask them to.

Everything that happens at the clinic is strictly confidential. No information is passed on to other doctors, to family members or to insurance companies. Occasionally, the doctors may need to communicate in confidence with other GUM clinics.

How long will you have to wait for an appointment?

Naturally, the rise in STD figures over the last decade has put GUM clinics under pressure. But the staff are doing their best to cope, and currently most people can be seen within 72 hours of contacting the clinic. On some days of the week, you may be able to just walk in and see a doctor quite rapidly.

In order to prevent the spread of infection: it's important that you don't have sex until you have been seen and diagnosed.

Finally, bear in mind that most STDs are easily cured. If you've taken a risk, go to a GUM clinic for a confidential chat and some tests.

The materials in this web site are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor. The web site does not have answers to all problems. Answers to specific problems may not apply to everyone. If you notice medical symptoms or feel ill, you should consult your doctor - for further information see our Terms and conditions.

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